This invention relates to a system for and a method of supplying fuel to an internal combustion engine mounted on an automobile.
In view of the emission which result from the burning of a petrochemical fuel and inefficiencies in the purification of exhaust gas, there has been an increasing interest in the type of internal combustion engine which uses, as a fuel, a mixture of gasoline and alcohol, such as methanol and ethanol, or uses a fuel such as alcohol instead of gasoline. One such engine is disclosed in Japanese Patent Unexamined Publication No. 62-243937.
In the above mentioned publication, consideration is not given to specific control for dealing with the case where fuel is changed from a mixed fuel of methanol and gasoline to a mixed fuel to ethanol and gasoline, and the case where the nature of the gasoline itself is greatly changed. Therefore, this proposed solution has a problem that it can not provide a system for satisfactorily effecting an accurate air-fuel ratio control.
And besides, a fuel sensor is known to become deteriorated upon lapse of time, so that its output is changed; however, there has not been proposed any specific means for detecting and correcting such changes. A fuel injection valve is also deteriorated upon lapse of time, and fails to supply fuel to an engine in accordance with a predetermined injection pulse duration or width; however, no means is provided for dealing with this problem. Further, when the octane value of gasoline in the mixed fuel is different, it is necessary to control the exhaust gas to a theoretical air-fuel ratio; however, no means is provided for dealing with this.
Not only in the case of using mixed fuel composed, for example, of alcohol and gasoline, but also in the case of using only gasoline as fuel, a fuel injection valve is usually mounted to be directed toward an intake valve. The direction of injection of the fuel from the fuel injection valve is in agreement with the direction of mounting of the fuel injection valve in the absence of any there is no influence by the air flowing through an intake pipe. Incidentally, the velocity of the air flowing through the intake pipe varies in accordance with the operating condition of the internal combustion engine. This velocity is low in a low-load operating condition of the engine, and is high in a high-load operating condition. Therefore, in actual practice, in the high-load operating condition, the direction of injection of the fuel from the fuel injection valve is affected by the air flow, and therefore is changed. Namely, the fuel injected from the fuel injection valve in the low-load operating condition is supplied to the intake valve, without being deflected by the air flow. On the other hand, in the high-load operating condition, there is encountered a problem that the fuel from the fuel injection valve is deflected by the air flow, so that the fuel is supplied out of registry with the intake valve.